First of all, let me explain what it means by a car's chassis. The chassis (usually made of steel) consists of the frame and mechanicals like engine, transmission and suspension. There are many types of chassis available in the market such as ladder frame, lightweight (Superleggera) frame, monocoque frame, so on and so forth.
A well weighted distribution of weight between the two axles can benefits the handling, stability, traction and acceleration of the car. Meanwhile, if a car’s chassis doesn’t have a well balanced weight distribution, the car can easily experience oversteer and understeer. Let’s say if the rear of a car doesn’t have enough weight, then the grip of the rear wheels will be reduced, so the car will tend to have oversteer where the rear wheels lose their traction. Therefore, it is said ideal if the weight distribution between the front and rear axle is distributed as equal as possible.
Maybe that's why BMW has been so consistent in offering 50:50 weight distribution for its products. Notice the overly long space between the front tyres and the front door of the BMWs? It is designed like that to have a better weight distribution on the chassis and for the optimum engine location for good weight distribution.
However, it's a different condition for a sports car. Many sports car manufacturers such as Porsche prefer to have rear weight bias, where some of the reasons are to have better corner entry and corner exit as well as better braking. Having more weight at the back (especially with rear engine placement) can benefit better braking where the rear tyres can be braked more efficiently instead of transferring all the weight to the front tyres and brakes while braking.
*Currently I'm doing Final Year Project on the weight distribution of car's chassis, so I'm sharing some of my understanding with you guys!
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